Setz appears to be using the European fire classifications, which are:

• Type A: Standard combustibles (wood, cloth, etc). Pouring water on it is enough to put it out.
• Type B: Flammable liquids (gasoline, etc). Water will only spread the fuel around, use an inhibitor like a fire extinguisher to smother the fire.
• Type C: Flammable gases (propane, etc). Similar to Type B (under the American system, both liquids and gases are considered type B), although there's probably also some gas leak that must be addressed as well.
• Type D: Flammable metals. The hardest to put out, as what will successfully suppress the fire differs depending on the metal. For example, some metals actually combust when exposed to water (hello, sodium), or with the chemicals in some fire extinguishers. Generally requires some type of dry powder extinguisher (IIRC chem labs often keep a bucket of sand around for this purpose).